The present invention generally relates to pressure vessels and, more specifically, to latch mechanisms adapted to seal the door of a pressure vessel, such as a sterilizer used in scientific applications and other medical applications.
Sterilizers and similar pressurized vessels typically include an outer housing which contains a chamber. The chamber has an access opening through which items are placed for sterilization within the chamber interior. Various apparatus and controls are provided for exposing the items within the chamber to sterilants under sterilizing conditions, often at elevated and/or reduced pressures. For example, during a typical sterilizing cycle, the chamber may experience portions of the cycle at elevated pressures and other portions of the cycle at reduced or vacuum pressures. A door is attached to the housing and is configured to cover the access opening. The door effects a pressure seal using a resilient gasket forming an interface between the door and the area of the chamber surrounding the access opening. Mechanical or pneumatic devices have been used to either expand or compress the gasket to effectively seal the access opening. Compression gaskets, as the name implies, operate under compression to seal the access opening, while other flexible pressure sealing gaskets are held in a sealing position by internal positive pressure within the chamber.
One problem with compression gaskets is that the user must either manually apply a large amount of force to close the latch of the door or tediously rotate a manual screw mechanism to obtain the required compression force against the seal. Furthermore, with the manual screw closure, there is a risk of over-tightening or under-tightening which, respectively, may reduce gasket life or result in leaks around the seal. A problem with flexible, positive pressure sealing gaskets is that, although these are simple and effortless to close, they may not be used in sterilizers that employ initial vacuum pulsing or final vacuum drying since they only seal with a positive internal pressure in the chamber. Another current design has the ability to open the door slightly after exposure to allow for improved convection in the chamber to enhance drying. This feature is used in sterilizers that do not employ a vacuum cycle within the chamber. These configurations are manually latched and sealed and use a solenoid to disengage the latch.
In view of various problems in the art, including those mentioned above, it would be desirable to provide a latch and closing mechanism for a pressure vessel that may be used under both positive and vacuum pressures, while also ensuring consistent seal compression during every use, even after seal wear.
To achieve these and other advantages, the present invention provides a pressure vessel especially useful in sterilizing procedures and including a pressurizable chamber housing having an interior for receiving items to be sterilized and further having an access opening to the chamber. Hinge structure connects a door to the chamber housing. The hinge structure facilitates movement of the door between an open condition, a latched condition and a latched and sealed condition with respect to the access opening. The door further includes latch structure for facilitating the latched condition. A seal is connected to at least one of the chamber housing and the door and is disposed in sealing engagement around the access opening when the door is in the latched and sealed condition. Finally, a powered drive mechanism with a movable output is mounted for operative connection with the latch structure or another part of the door such that powered movement of the output moves the door from the initially latched condition to the latched and sealed condition. The powered drive mechanism uses an actuator, such as a motor or a linear drive device. In another general aspect, a sensor is used to stop the actuator at a consistent seal compression level. The sensor may take on many different forms as those of ordinary skill will recognize and may comprise one sensing component or multiple components acting together as a sensor for this purpose.
As a more specific feature of the preferred embodiment, the drive mechanism includes a motor with a rotatable output. A motor control and sensor are coupled with the motor to sense an amount of compression being applied by the motorized drive mechanism to the seal. At a predetermined compression level, the motor control deactivates the motor. As illustrative examples, the motor may be a DC gear motor or other automatic drive device for supplying a linear actuation and the sensor may be an electric current sensor of many different possible designs. In a configuration utilizing a DC motor, a variance in the torque of the motor output will correspond directly with a variance in the electric current drawn by the motor. This is used as the preferred manner of detecting and controlling the amount of compression being applied to the seal since the motor may be operated by the motor control consistently to reach the same torque level and, therefore, the same seal compression level. Therefore, the seal will not be over-tightened or under-tightened. Another main advantage of this system is that seal wear will automatically be compensated for by the motor control and sensor due to the fact that the door is not closed to a fixed position, but rather to a fixed compression or motor torque.
In the preferred embodiment, the motorized drive mechanism further comprises a yoke connected with the rotatable motor output such that rotation of the output translates or, in other words, generally moves the yoke in a linear manner. Other closing mechanisms may be incorporated in the mechanical design as well. These might include cam mechanisms, rotary mechanisms and other mechanical systems that may, for example, rely on vacuum pressure in the chamber to at least assist in obtaining a sealed condition. The yoke is further adapted to be connected with the latch structure of the door in the latched condition such that translation of the yoke by the rotatable output moves the door to the latched and sealed condition. As one example, the motor output may include a threaded shaft and the yoke may include an internally threaded hole for receiving the threaded shaft. The latch structure may further comprise a movable handle and at least one engagement member connected for movement by the handle between latched and unlatched conditions. The engagement member is adapted to connect with the motorized drive mechanism in the latched condition and, more specifically, to the yoke via a pair of pins.
As another feature of the invention, a stop member is provided to prevent unlatching in the latched and sealed condition. This feature may be used to advantage in manual latch and seal configurations as well as the automatic or powered system as generally described herein. The engagement member includes a stop member configured to prevent movement of the engagement member to the unlatched condition when the door is in the latched and sealed condition. Since the pins will be frictionally engaged in holes contained in the yoke when latched, this frictional engagement will also help prevent unlatching, especially when the interior of the chamber housing is under positive pressure.
Since the door is closed with the use of a motorized screw shaft or other comparable element, it cannot be opened until the screw shaft is rotated to disengage the door. This provides the ability to lock the door with electrical motor controls to fully meet sterilization standards. The user will not be able to open the door until the sterilization cycle has completed and the motor, such as a gear motor, operates to release the latch structure.
These and other features, advantages and objectives of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings.